Methods of depositing antimony-comprising phase change material onto a substrate and methods of forming phase change memory circuitry

ABSTRACT

A method of depositing an antimony-comprising phase change material onto a substrate includes providing a reducing agent and vaporized Sb(OR) 3  to a substrate, where R is alkyl, and forming there-from antimony-comprising phase change material on the substrate. The phase change material has no greater than 10 atomic percent oxygen, and includes another metal in addition to antimony.

TECHNICAL FIELD

Embodiments disclosed herein pertain to methods of depositingantimony-comprising phase change material onto a substrate and tomethods of forming phase change memory circuitry.

BACKGROUND

Integrated circuit memory may be characterized as being either volatileor non-volatile. Volatile memory must be reprogrammed/rewritten,typically multiple times per second, due to charge dissipation.Non-volatile memory, on the other hand, can maintain any of itsprogrammed states without necessarily requiring periodic refresh.Example volatile memory includes Dynamic Random Access Memory (DRAM).Example non-volatile memory includes Static Random Access Memory (SRAM),Flash Memory, and Phase Change Memory (PCM).

There is a continuing goal in the fabrication of integrated circuitry tomake individual devices smaller to increase the density of thecircuitry, and thereby either reduce the size of the circuitry or enablemore circuitry to be packed into a smaller space. Yet, the smaller anddenser circuitry must be reliable in operation. Phase change memory isof increasing interest due to its apparent ability to be scaled smallerand maintain reliability.

The primary components of phase change memory are a pair of electrodeshaving a phase change material sandwiched there-between. The phasechange material is capable of being selectively modified in a mannerthat changes its electrical resistance between at least high and lowresistant states which can be “read” and therefore used as solid-statememory. In phase change memory, electric currents of differentmagnitudes are selectively passed to the phase change material whichchanges the resistance of the material very rapidly.

Phase change materials are often formed of a combination or alloy ofdifferent metals. One metal of interest is antimony. Such might becombined, for example, with one or both of germanium and tellurium toform a GeSb, SbTe, or GeSbTe alloy. Chemical vapor deposition is onemethod by which such phase change materials may be deposited over asubstrate. For example, different deposition precursors comprising oneeach of germanium, antimony and tellurium may be provided in desiredquantities over a substrate under suitable conditions such that a GeSbTealloy is deposited having desired quantities of the respectivegermanium, antimony and tellurium. Example antimony precursors includetris dimethylamino antimony and organometallics such as tris isopropylantimony. Such precursors may, however, require substrate temperaturesin excess of 400° C. to achieve adequate deposition when used inchemical vapor or atomic layer deposition also using NH₃. Suchtemperatures may be incompatible with features on the substrates, orwith other precursors, for example tellurium precursors. Use oftemperatures lower than 400° C. may result in no deposition, less thandesired deposition, or an unacceptably slow rate of deposition.

Phase change materials may also be used in fabrication of rewritablemedia, for example rewritable CDs and DVDs.

While embodiments of the invention were motivated in addressing theabove-identified issues, the invention is in no way so limited.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic sectional view of a substrate in process inaccordance with an embodiment of the invention.

FIG. 2 is a view of the FIG. 1 substrate at a processing step subsequentto that shown by FIG. 1.

FIG. 3 is a diagrammatic sectional view of a substrate in process inaccordance with an embodiment of the invention.

FIG. 4 is a view of the FIG. 3 substrate at a processing step subsequentto that shown by FIG. 3.

FIG. 5 is a view of the FIG. 4 substrate at a processing step subsequentto that shown by FIG. 4.

FIG. 6 is a view of the FIG. 5 substrate at a processing step subsequentto that shown by FIG. 5.

FIG. 7 is a diagrammatic sectional view of a substrate in process inaccordance with an embodiment of the invention.

FIG. 8 is a view of the FIG. 7 substrate at a processing step subsequentto that shown by FIG. 7.

FIG. 9 is a view of the FIG. 8 substrate at a processing step subsequentto that shown by FIG. 8.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Embodiments of the invention encompass methods of depositing anantimony-comprising phase change material onto a substrate. Suchincludes providing a reducing agent and vaporized Sb(OR)₃ to asubstrate, where R is alkyl, and forming there from antimony-comprisingphase change material on the substrate. Some example Sb(OR)₃ materialsare Sb(OC₂H₅)₃, Sb(OCH₃)₃, Sb(OC₃H₇)₃, and Sb(OC₄H₉)₃. The phase changematerial has no greater than 10 atomic percent oxygen and comprisesanother metal in addition to antimony. In one embodiment, the phasechange material which is formed has no greater than 5 atomic percentoxygen, and in one embodiment no greater than 1 atomic percent oxygen.Ideally, the phase change material is formed to have no detectableoxygen present therein. Regardless, in one embodiment, the substratetemperature while the reducing agent and the vaporized Sb(OR)₃ areprovided to the substrate is no greater than 450° C.

The reducing agent and the Sb(OR)₃ may be provided to the substrate atthe same time, and/or at different times. Regardless, example techniquesinclude chemical vapor deposition (CVD) and atomic layer deposition(ALD), including a combination of ALD and CVD methods. Further, anydeposition may be plasma enhanced, or conducted in the absence ofplasma. Any existing or yet-to-be developed reducing agent capable ofremoving at least some of the alkoxy ligands from the antimony may beused, with NH₃, H₂, CH₂O, and CH₂O₂ being examples. Multiple of theseand/or additional reducing agents may be used.

In some embodiments, example metals in addition to antimony in formingan antimony-comprising phase change material include one or both of Geand Te. Example germanium precursors include tetrakis-dimethylamidogermanium, germanium halides (i.e., GeCl₄), germanium hydride (GeH₄),tetrakis-trimethylsilyl germanium, tetraalkyl germanes (i.e., Ge(CH₃)₄),and amindinates (i.e., bis(N,N′-diisopropyl-N-butylamidinate) germanium(II)). Analogous compounds incorporating tellurium instead of germaniummay be used as tellurium precursors. In chemical vapor deposition, suchadditional precursors in one embodiment are provided to the substrate atthe same time as providing the Sb(OR)₃ to the substrate. Relativeportions of the Sb(OR)₃, Ge-comprising precursor, and Te-comprisingprecursor can be used to impart desired atomic quantity of Sb, Ge, andTe in the resulting material. One specific example is Ge₂Sb₂Te₅. Otherexample metals in addition to antimony include selenium, indium,gallium, boron, tin, and silver. Some nitrogen and silicon mightadditionally be present.

An example temperature range for the substrate during formation of theantimony-comprising phase change material is from 200° C. to 450° C.Where tellurium precursors are being used, an example substratetemperature range is from 300° C. to 360° C. An example pressure rangeis from 10⁻⁶ Torr to atmospheric pressure. In one embodiment, an examplechemical vapor deposition pressure range is from 1 mTorr to 10 Torr. Inone embodiment, an example atomic layer deposition pressure range isfrom 0.1 mTorr to 1 Torr.

An example embodiment of a method of depositing an antimony-comprisingphase change material onto a substrate is described with reference toFIGS. 1 and 2. FIG. 1 depicts a substrate 10 over which anantimony-comprising phase change material will be deposited. Substrate10 might comprise any substrate, including semiconductor substrates. Inthe context of this document, the term “semiconductor substrate” or“semiconductive substrate” is defined to mean any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” refers to any supporting structure,including, but not limited to, the semiconductive substrates describedabove. Substrate 10 may be a suitable substrate to be used in formationof rewritable optical media, for example CDs and DVDs. Regardless, anyexisting or yet-to-be developed substrate 10 may be used.

FIG. 1 depicts an embodiment wherein both Sb(OR)₃ and one or morereducing agents (R.A.) are provided over substrate 10 at the same time.For example, such might occur by CVD in any suitable chamber, and underconditions which the precursors combine at or above the surface ofsubstrate 10 to deposit an antimony-comprising phase change material 12thereover (FIG. 2). For example, Sb(OR)₃ can be provided as a liquid ina vaporizer, with an inert gas flowed thereover to carry Sb(OR)₃ vaporto substrate 10 within a deposition chamber. Example carrier gasesinclude helium, argon, and N₂. In a single wafer processer having aninternal chamber volume of from about 2 to 3 liters, an example flowrate of a carrier gas is from 20 sccm to 50 sccm. An example flow ratefor the reducing agent is from 500 sccm to 5 slm. Plasma may or may notbe used.

A precursor comprising one or more additional metals other than antimonymay also be provided within the chamber at the same time with theSb(OR)₃ to incorporate such additional metal(s) within material 12.Alternately or in addition thereto, such could be provided subsequent toprovision of the Sb(OR)₃ within the chamber. Further by way of example,sequential/pulsed CVD may be used. For example, Sb(OR)₃ and/or aprecursor containing an additional metal could be fed to the substratesurface in the absence of a reducing agent wherein physisorption of theprecursor(s) occurs to the substrate. This could be followed by flowingone or more reducing agents to the substrate to deposit the desiredantimony-comprising phase change material onto the substrate.

In a specific example in formation of an antimony andgermanium-comprising phase change material, a substrate was positionedupon a chuck within a deposition chamber, with the chuck being heated toabout 360° C. Pressure within the chamber was 1 Torr. Liquid Sb(OC₂H₅)₃was provided in a vaporizer/bubbler at 90° C. and liquidbis(N,N′-diisopropyl-N-butylamidinate) germanium (II) provided inanother vaporizer/bubbler at 95° C. Argon as a carrier gas was flowedthrough each of the vaporizers at 50 sccm and then to the depositionchamber. NH₃ was also flowed to the deposition chamber at 2000 sccm. Anantimony and germanium-comprising phase change material was depositedupon the substrate. The deposited layer had no detectable oxygenpresent.

An example ALD method is next described with reference to FIGS. 3-6. ALDinvolves formation of successive atomic layers on a substrate. Suchlayers may comprise an epitaxial, polycrystalline, amorphous, etc.material. ALD may also be referred to as atomic layer epitaxy, atomiclayer processing, etc. Described in summary, ALD includes exposing aninitial substrate to a first chemical specie to accomplish chemisorptionof the specie onto the substrate. Theoretically, the chemisorption formsa monolayer that is uniformly one atom or molecule thick on the entireexposed initial substrate. In other words, a saturated monolayer isformed. Practically, as further described below, chemisorption might notoccur on all portions of the substrate. Nevertheless, such an imperfectmonolayer is still a monolayer in the context of this document. In manyapplications, merely a substantially saturated monolayer may besuitable. A substantially saturated monolayer is one that will stillyield a deposited layer exhibiting the quality and/or properties desiredfor such layer.

The first specie is purged from over the substrate and a second chemicalspecie is provided to react with the first monolayer of the firstspecie. The second specie is then purged and the steps are repeated withexposure of the second specie monolayer to the first specie. In somecases, the two monolayers may be of the same specie. As an option, thesecond specie can react with the first specie, but not chemisorbadditional material thereto. That is, the second specie can cleave someportion of the chemisorbed first specie, altering such monolayer withoutforming another monolayer thereon. Also, a third specie or more may besuccessively chemisorbed (or reacted) and purged just as described forthe first and second species.

Purging may involve a variety of techniques including, but not limitedto, contacting the substrate and/or monolayer with a purge gas and/orlowering pressure to below the deposition pressure to reduce theconcentration of a specie contacting the substrate and/or chemisorbedspecie. Examples of purge gases include N₂, Ar, He, etc. Purging mayinstead include contacting the substrate and/or monolayer with anysubstance that allows chemisorption byproducts to desorb and reduces theconcentration of a contacting specie preparatory to introducing anotherspecie. The contacting specie may be reduced to some suitableconcentration or partial pressure known to those skilled in the artbased on the specifications for the product of a particular depositionprocess.

ALD is often described as a self-limiting process, in that a finitenumber of sites exist on a substrate to which the first specie may formchemical bonds. The second specie might only bond to the first specieand thus may also be self-limiting. Once all of the finite number ofsites on a substrate are bonded with a first specie, the first speciewill often not bond to other of the first specie already bonded with thesubstrate. However, process conditions can be varied in ALD to promotesuch bonding and render ALD not self-limiting. An example would be anALD process where insufficient purging is employed such that some CVDoccurs. Accordingly, ALD may also encompass a specie forming other thanone monolayer at a time by stacking of a specie, forming a layer morethan one atom or molecule thick.

The general technology of CVD includes a variety of more specificprocesses, including, but not limited to, plasma enhanced CVD andothers. CVD is commonly used to form non-selectively a complete,deposited material on a substrate. One characteristic of CVD is thesimultaneous presence of multiple species in the deposition chamber thatreact to form the deposited material. Such condition is contrasted withthe purging criteria for traditional ALD wherein a substrate iscontacted with a single deposition specie that chemisorbs to a substrateor reacts with a previously deposited specie. An ALD process regime mayprovide a simultaneously contacted plurality of species of a type orunder conditions such that ALD chemisorption, rather than CVD reactionoccurs. Instead of reacting together, the species may chemisorb to asubstrate or previously deposited specie, providing a surface onto whichsubsequent species may next chemisorb or react to form a complete layerof desired material. Under most CVD conditions, deposition occurslargely independent of the composition or surface properties of anunderlying substrate. By contrast, chemisorption rate in ALD might beinfluenced by the composition, crystalline structure, and otherproperties of a substrate or chemisorbed specie. Other processconditions, for example, pressure and temperature, may also influencechemisorption rate.

Referring to FIG. 3, vaporized Sb(OR)₃, where R is alkyl, is providedover substrate 10 in the absence of the reducing agent. Such has beeneffective to form a monolayer 20 comprising Sb(OR)_(x) onto substrate 10from the Sb(OR)₃, where “x” is less than 3.

Referring to FIGS. 4 and 5, a reducing agent (R.A.) is provided tosubstrate 10 having monolayer 20 received thereover (FIG. 4) underconditions suitable to remove OR ligand (FIG. 5) from the Sb, therebyforming a monolayer 22 comprising Sb. Any one of combination of theabove reducing agents may be used

As a specific example, a substrate was positioned upon a chuck within adeposition chamber, with the chuck being heated to about 360° C.Pressure within the chamber was 1 mTorr. Liquid Sb(OC₂H₅)₃ was providedin a vaporizer/bubbler at 85° C. Argon as a carrier gas was flowedthrough the vaporizer at 50 sccm and to the deposition chamber for 2seconds. Argon flow was then ceased, and the chamber pumped out for 15seconds. Alternately or additionally, purge gas may be flowed throughthe deposition chamber. Such was followed by flowing NH₃ at 2000 sccmfor 2 seconds, followed by pumping out for 15 seconds.

FIG. 6, by way of example only, depicts a monolayer 24 comprisingTeR_(x) over monolayer 22. Such may be formed by feeding a suitabletellurium-comprising precursor to the substrate. Such may be followed byfeeding of a suitable reducing agent to the substrate to remove R_(x)ligand from the Te, thereby forming a layer comprising Sb and Te. Suchcould be repeated multiple times with one or both of Sb(OR)₃ andtellurium-comprising precursors (and/or other precursors) to deposit adesired antimony-comprising phase change material over substrate 10. Forexample, such may be used to produce an antimony and tellurim comprisingphase change material having no detectable oxygen present therein. Otherprecursors including other metals, for example germanium, could also beprovided depending on the composition of the antimony-comprising phasechange material being formed. Further and regardless, a combination ofCVD and ALD techniques may be used.

Embodiments of the invention also encompass methods of forming phasechange memory circuitry, for example as shown and described withreference to FIG. 7-9. Referring to FIG. 7, such depicts a substratefragment 30 comprising a semiconductor substrate 32, for examplemonocrystalline silicon. A conductively doped diffusion region 34 hasbeen formed within semiconductor material of semiconductor substrate 32.A suitable dielectric 36 has been formed thereover, and an opening 38formed there-through to diffusion region 34. Example suitable dielectricmaterials include silicon dioxide and/or silicon nitride whether dopedor undoped.

Inner electrode material 40 has been formed within opening 38 and inconductive electrical connection with diffusion region 34. Bottomelectrode 40 may or may not be homogenous, with tungsten and titaniumnitride being example conductive materials.

Referring to FIG. 8, an antimony-comprising phase change material 50 hasbeen deposited over inner electrode material 40. Such may be depositedby any of the techniques described above, and accordingly has no greaterthan 10 atomic percent oxygen and includes another metal in addition toantimony.

Referring to FIG. 9, outer electrode material 60 has been formed overantimony-comprising phase change material 50, thus forming a phasechange memory cell 75. Outer electrode material 60 may be the same ordifferent as that of the composition of inner electrode material 40.Antimony-comprising phase change material 50 is shown as being formed indirect physical touching contact with each of inner electrode material40 and outer electrode material 60, although other embodiments arecontemplated. The circuitry may be configured such that one or both ofelectrode materials 40 and 60 function as the programming electrodewhereby a suitable programmable volume of antimony-comprising phasechange material 50 between inner electrode material 40 and outerelectrode material 60 is switchable between high and low resistanceprogramming states by application of suitable currents, as in existingor yet-to-be developed technology.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

1. A method of depositing an antimony-comprising phase change materialonto a substrate, comprising providing a reducing agent and a vaporizedcompound consisting of Sb(OR)₃ to the substrate, where R is an alkyl,and forming there-from the antimony-comprising phase change material onthe substrate, the antimony-comprising phase change material having nogreater than 10 atomic percent of oxygen and comprising another metal inaddition to antimony.
 2. The method of claim 1 wherein a substratetemperature while the reducing agent and the vaporized Sb(OR)₃ areprovided to the substrate is no greater than 450° C.
 3. The method ofclaim 1 wherein the forming produces the antimony-comprising phasechange material to have no greater than 5 atomic percent of the oxygen.4. The method of claim 1 wherein the forming produces theantimony-comprising phase change material to have no greater than 1atomic percent of the oxygen.
 5. The method of claim 1 wherein theforming produces the antimony-comprising phase change material to haveno detectable oxygen therein.
 6. The method of claim 1 wherein thereducing agent and the Sb(OR)₃ are provided to the substrate at a sametime.
 7. The method of claim 1 wherein the reducing agent comprises atleast one of NH₃, H₂, CH₂O, and CH₂O₂.
 8. The method of claim 1 whereinthe reducing agent and the Sb(OR)₃ are provided to the substrate atdifferent times.
 9. The method of claim 1 wherein the another metalcomprises Ge.
 10. The method of claim 1 wherein the another metalcomprises Te.
 11. The method of claim 1 wherein the another metalcomprises Ge and Te.
 12. The method of claim 1 wherein the another metalcomprises at least one of In, Se, Ga, B, Sn, and Ag.
 13. The method ofclaim 1 wherein the forming comprises chemical vapor deposition.
 14. Themethod of claim 13 wherein the chemical vapor deposition is in anabsence of plasma.
 15. The method of claim 13 wherein the chemical vapordeposition is plasma enhanced.
 16. The method of claim 13 wherein theanother metal comprises Ge, and the method further comprises providing aGe-comprising precursor to the substrate at a same time as providing theSb(OR)₃ to the substrate.
 17. The method of claim 13 wherein the anothermetal comprises Te, and the method further comprises providing aTe-comprising precursor to the substrate at a same time as providing theSb(OR)₃ to the substrate.
 18. The method of claim 13 wherein the anothermetal comprises Ge and Te, and the method further comprises providingboth a Ge-comprising precursor to the substrate and a Te-comprisingprecursor to the substrate at a same time as providing the Sb(OR)₃ tothe substrate.
 19. The method of claim 1 wherein the forming comprisesatomic layer deposition.
 20. The method of claim 1 wherein the formingof the antimony-comprising phase change material comprises: forming amonolayer onto the substrate from the Sb(OR)₃; and after forming themonolayer, providing the reducing agent to the monolayer to removeligands consisting of OR from the Sb to produce an Sb monolayer on thesubstrate.
 21. A method of forming phase change memory circuitry,comprising: forming an inner electrode material over a substrate;depositing an antimony-comprising phase change material over the innerelectrode material, the depositing comprising providing a reducing agentand a vaporized compound consisting of Sb(OR)₃ over the inner electrodematerial, where R is an alkyl, and forming there-from theantimony-comprising phase change material over the inner electrodematerial, the antimony-comprising phase change material having nogreater than 10 atomic percent of oxygen and comprising another metal inaddition to antimony; and forming an outer electrode material over theantimony-comprising phase change material.
 22. The method of claim 21comprising forming the antimony-comprising phase change material indirect physical touching contact with the inner electrode material, andforming the outer electrode material in direct physical touching contactwith the antimony-comprising phase change material.
 23. The method ofclaim 21 wherein forming the antimony-comprising phase change materialproduces the antimony-comprising phase change material to have nogreater than 1 atomic percent of the oxygen.
 24. The method of claim 21wherein forming the antimony-comprising phase change material producesthe antimony-comprising phase change material to have no detectableoxygen therein.
 25. The method of claim 21 wherein the forming of theantimony-comprising phase change material comprises: forming a monolayeronto the substrate from the Sb(OR)₃; and after forming the monolayer,providing the reducing agent to the monolayer to remove ligandsconsisting of OR from the Sb to produce an Sb monolayer on thesubstrate.